1. Field
Example embodiments relate to a method of forming wires of a semiconductor device, for example, a method of forming wires of a semiconductor device in which a heat treatment process may be applied to a damascene structure wire to increase the reliability of the wire.
2. Description of the Related Art
As semiconductor devices become more highly integrated and are required to operate at higher speeds, metal wire structures having a lower resistance may be needed. For example, as the integration density of semiconductor devices increases, the structure of the metal wire may become more complicated.
Thus, a multiple metal wire structure may be used in which metal lines may be stacked in multiple layers. A metal having lower resistance may be required to form electric wires having a fine line width without degrading a response speed, and the wiring may be formed in a multilayer structure to increase integration density.
Of the metals having a lower resistance, copper may be used to replace a conventional metal wire formed of aluminum. However, copper may not be readily patterned by photolithography and etching processes. Accordingly, a damascene process in which, after copper may be buried in a via hole and a trench using a plating method, a via plug and a metal line may be formed by planarizing the resultant product.
In a conventional damascene metal wire process, a barrier metal film may be formed to prevent a metal wire from being diffused into an inter-insulating film after a via hole and trench are formed. The barrier metal film may be a nitride metal film formed of TaN, TiN, etc. However, the nitride metal film may have a specific resistance larger than a pure metal film. Therefore, the nitride metal film may increase a contact resistance between the via plug and the metal wire, and may degrade the response speed of the semiconductor device. Accordingly, after forming the barrier metal film, a process of removing or minimizing the thickness of the barrier metal film in a region where the via plug contacts the metal wire may be applied to reduce the contact resistance between the via plug and the metal wire. The barrier metal film removed from the contact region may be deposited on a sidewall of the via plug and may be formed into a barrier metal spacer.
However, the process of forming the barrier metal spacer by etching the barrier metal film may expose the metal wire below the barrier metal film, and etching damage may occur on an exposed surface of the metal wire. Thus, the surface roughness of the metal wire may be increased. If the roughness of the surface of the metal wire is increased, electro-migration of the metal wire by electrical stress may be accelerated, which may result in the generation of voids in the contact of the metal wire in a short period of time near.
FIG. 1 illustrates a vertical-scanning electron microscopy (V-SEM) image of a cross-section of a metal wire formed using a conventional technique after electrical stress is applied to the metal wire. Referring to FIG. 1, a void 10 may be generated in a metal wire below a region where a contact between the via plug and the metal wire may be formed. The void 10 may be generated due to the electro-migration of the metal wire, and may reduce the reliability of the wire.